1. Field of the Invention
The present invention relates in general to wall systems for clean rooms. More specifically, but without restriction to the particular use which is shown and described, this invention relates to non-progressive clean room wall systems having wall heights greater than eight feet.
2. Description of the Related Art
There is an increasing need for cleaner environments in which laboratory procedures and high technology component production, such as, semiconductor chip manufacture, may be undertaken. Clean room wall systems, such as the Slimline 200 wall system, manufactured by Unistrut Corporation, provide a suitably clean environment and allow for a variety of wall configurations depending on the particular application. There is also a need for clean room wall systems that are non-progressive, that is, wall systems where the wall panels are demountable from the wall without having to tear down or remove an adjacent panel.
The non-progressive wall assembly generally consists of framing members, panel retainers and wall panels. The framing members are the horizontal and vertical support posts that provide the wall system with its structural integrity. Attached to the framing members are the panel retainers, also known as battens. The battens capture the wall panels, permit components to be mounted onto the wall, and serve as trim to cover the framing members and the junctures between the framing members. It is the battens in a non-progressive wall system that permit the removal of single wall panels in a continuous wall without removing the adjacent panels or the framing members. The wall panels of a cleanroom wall assembly can be made of various materials so long as the material is non-particulating and non-off-gassing. For a disclosure of non-progressive clean room wall systems, U.S. Pat. No. 5,414,967, issued May 16, 1995, and U.S. Pat. No. 5,307,600, issued May 3, 1994, both assigned to Unistrut International Corporation, are incorporated herein by reference.
Traditionally, clean room wall systems were manufactured for wall heights of 8 to 9 feet. The wall systems designed for these heights could accommodate the lateral loads and deflection limits required by users of these wall systems. However, with the desire for wall systems to accommodate wall heights of 11 to 12 feet, new designs are now needed to provide for this wall height and yet maintain specific loading and deflection requirements.
Specifically, clean room wall systems of 11 to 12 feet must be designed to handle lateral loads of approximately 5 pounds per square feet with a deflection of L/120 or less--L being defined as the wall height in inches. Moreover, the wall systems for 12 foot ceiling heights need to allow for the removal of a lower section of the wall below a chosen elevation, for example at the 8 foot level, while leaving the upper wall section structurally intact. At the 8 foot level, the wall system still must withstand the moment conditions created at that level. One design that has been mostly successful in fulfilling these requirements is installing at the 8 foot level, a horizontal header that extends the entire length of the wall system and mounting 3 or 4 foot panels and framing members above the horizontal header. However, this design fails from a practical standpoint in that equipment taller than 8 feet cannot fit through the wall because of the horizontal continuous header at the 8 foot level. Because of this horizontal continuous header, excessive demolition of the wall system is required, including the removal of several adjacent panels. This extra demolition and panel removal defeats the purpose and intent of a non-progressive wall system and creates an objectionable amount of contamination of the work space by airborne particles and other debris.